Does tuna contain methylmercury?
Almost all ocean fish and seafood naturally contain minute amounts of methylmercury, due in part to underwater volcanic activity. But the amount in light canned tuna is exceedingly low. In fact, when the Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) issued new advice about the best ways to limit methylmercury in the diet, FDA and EPA listed light canned tuna as one of the commonly eaten fish that contains very low levels of mercury.
Although canned albacore tuna contains somewhat more mercury than canned light tuna, the amount is still very low and well below government standards. That is why the new government advisory tells pregnant women that they can safely eat up to 6 ounces of albacore tuna in a week. In general, there are 2 ounces of canned albacore in a typical serving.